[V8] Fuel pressure gauge

[Scott Phillips]

Fuel pressure would be fractionally higher on the line than the rail,
depending on the placement of the gauge it is contending with the
operation of the injectors. However it is the job of the pressure
regulator, fuel pump and return circuit that maintains that pressure. 

Scott

-----Original Message-----
From: v8-bounces at audifans.com [mailto:v8-bounces at audifans.com] On Behalf
Of Scott Simmons
Sent: Tuesday, February 13, 2007 5:18 PM
To: d saad
Cc: v8 at audifans.com
Subject: Re: [V8] Fuel pressure gauge

Most that I've seen are on the rail.  How do pressure change compared to

pressure in the rail and pressures on an input line?  Would not the 
input line be higher pressure than the rail?

~SS

d saad wrote:

>You have a few options -
>
>-> Buy a fuel pressure tester that
>comes with the adapters. Expensive, but maybe worth it for the
>convenience.
>-> install a permanent test port - like most cars now
>have
>-> go to the junk yard and get some fittings and make your
>own adapter.
>
>I did both the junkyard thing, and then put in a
>permanent test port. Both were easy to do, but take time. To scavenge
>junkyard parts, all I did was find some appropriate fittings, and
attach
>them to a brass tee which had a standard Ford style schrader valve in
it.
>
>
>I decided to do the permanent port when my flex line from the
>right shock tower to the fuel rail started to leak. There is some risk
>with this one - but mine has been there for many years now and I have
had
>no problems. Here is a short description on how to do it:
>http://www.icehouse.net/dsaad/
>This required me to have new hose
>crimped on - because the soldering will destroy the old hose. It took
the
>guy at the hose shop a few tries to get it right, but it was cheap.
>
>
>Dave
>
>  
>
>><snip>Has anyone installed a
>>    
>>
>valve on the fuel rail to measure fuel
>  
>
>>pressure? I thought I
>>    
>>
>read about it somewhere.  The AF TWiki has one for
>  
>
>>S4/S6 cars. 
>>    
>>
>It was an incredibly valuable tool on my previous cars and
>  
>
>I'd
>  
>
>>like to have one to check numbers. <unsnip>
>>
>>    
>>
>
>  
>
>>Yes, I've installed a fitting on my S6.  I've also seen folks
>>    
>>
>who have
>  
>
>>modified their V8 fuel rail for the fitting.  I cut a
>>    
>>
>rubber section of
>  
>
>>the
>>fuel line near the fuel filter,
>>    
>>
>installed a brass tee with two
>  
>
>>hose-to-pipe-thread fittings. The
>>    
>>
>third leg of the tee to a brass Schrader
>  
>
>>valve.  You have to use
>>    
>>
>FI hose clamps on the hoses and a metal valve cap
>  
>
>>on
>>
>>    
>>
>the Schrader valve. The valve has a 1/4" flare fitting that's the
>  
>
>>most-common standard for EFI pressure gauges. The magic part is the
>>    
>>
>valve
>  
>
>>and it's NAPA # 209459 and I paid $3.74, (jobber price).
>>    
>>
>FI clamps are
>  
>
>>705-1226 or 1227 depending on hose diameter (14 mm
>>    
>>
>and 15 mm).  I've often
>  
>
>>wondered why so many guys on the list
>>    
>>
>just replace the FPR without
>  
>
>>checking
>>the pressure. 
>>    
>>
>FI pressure is critical, the ECM accepts it as a given
>  
>
>>pressure
>>    
>>
>and if it's off open-loop will be fat or lean and closed loop may
>  
>
>>not be able to squeeze the injectors enough to keep the engine
>>    
>>
>from
>  
>
>>running
>>fat.
>>Craig N.
>>90 V8
>>    
>>
>Q
>  
>
>>95 S6 Avant
>>
>>
>>    
>>
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>
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>>    
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>>    
>>
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>  
>
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>  
>
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>>    
>>
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>>    
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